Historically, methods for determining consumption of lubrication oil in a lubrication system for a gas turbine engine have been inaccurate due to the lack of automatic sensors and real-time monitoring. These methods have relied on manually-entered records of the amount of lubrication oil added, and these typically have comprised approximations. In addition, the hours of engine operation have been estimates based on aircraft utilisation. Therefore, the methods used to determine engine lubrication oil consumption have generally been based on approximate quantities of oil added and approximate hours of engine operation.
The inaccurate determination of oil consumption has contributed to early APU removals due to High Oil Consumption. Frequently, these APUs were returned to Repair Stations, where expensive repairs were performed, which could have been deferred to a later date had the High Oil Consumption condition not existed.
With the introduction of lubrication oil level sensors that accurately indicate engine lubrication oil quantity in real time and the ability to track actual engine operating hours, it is possible to more accurately determine engine lubrication oil consumption. Furthermore, the ability to communicate engine lubrication oil quantity and engine operating hours in real time to an engine data acquisition system for automatic retrieval can enable a prognostic and diagnostic health management system to monitor such lubrication oil consumption.